Mudskippers are interesting because they are a fish, but yet they spend most of their time on the land.
They still have gills, but they have pouches surrounding their gills that hold water which they breathe from... sort of like how a SCUBA diver takes air with them underwater: a mudskipper takes water with them above water.
They can also breathe cutaneously, like amphibians.
Interesting, huh?
Are they transitional forms? Have they been changing, and if so, from what? Weren't we told land animals came from fish, originally? Are these animals just late bloomers?
Some "living fossils" haven't changed much since first appearing in the fossil record... the horseshoe crab is one such critter... it first started appearing in the fossil record 435 million years go, we're told.
Fossil
Modern, Living Animal
It is so ancient, it has blue, copper-based blood, unlike the red, iron-based blood seen in higher, "more recent" species.
"The observation that species are amazingly conservative and static entities throughout long periods of time has all the qualities of the
emperors' new clothes: everyone knew it but preferred to ignore it. Paleontologists, faced with a recalcitrant record obstinately refusing to yield Darwin's predicted pattern, simply looked the other way" -
Eldredge and Tattersall,
The Myths of Human Evolution, 1982, p 45-46